Amino Acids, Peptides, pH, pI

Question 1

Amino Acid structure

Answer 1

amino (+) and carboxyl (-) grops
side chains (R)
C alpha carbon

linked via peptide bonds

numbering/naming starts at amino terminus

Question 2

Nonpolar, alipathic (7)

Answer 2

Glycine, alanine, proline, valine, leucine, isoleucine, methionine

Question 3

aromatic (3)

Answer 3

phenylalanine, tyrosine, tryptophan

Question 4

Polar uncharged (5)

Answer 4

serine, threonine, cysteine, asparagine, glutamine

can form hydrogen bonds, cysteine can disulfide bonds

Question 5

Positive (3)

Answer 5

lysine, arginine, histidine

Question 6

negative (2)

Answer 6

aspartate, glutamate

Question 7

Henderson Hasselbach

Answer 7

pH = pKa+log[A-]/[HA]

strong acid = large Ka = small pKa
amino acids can act as buffers, with two buffer regions bc of the carboxyl and amino groups separately

Question 8

Bicarbonate buffering

Answer 8

pH= 6.1+log[HCO3-] / [.03][PCO2]

metabolic acidosis: pH < 7.35 (low [HCO3-]
alkalosis pH >7.45

Question 9

pI

Answer 9

amino acids have charge of 0 at pI: zwitterions

AA is least soluble in water and does not migrate in electric field